At least seven people have been killed and 48 others injured in an explosion that rocked Venezuela's biggest oil refinery.

Amuay factory in the north of the country has a capacity of 645,000 barrels per day and the explosion was caused by a gas leak, according to the authorities.

"A cloud of gas exploded ... it was a significant explosion, there are appreciable damages to infrastructure and houses opposite the refinery," Rafael Ramirez, Venezuela's Energy Minister told state TV.

Rescue operations are under way and the injured are being evacuated from the area.

Meanwhile, authorities have ruled out the possibility of another explosion.

"There's no risk of another explosion. Right now, we're attending to the injured," Local Falcon state governor Stella Lugoshe told state TV.

Amuay, which is a natural bay, is part of the Paraguana Refining Centre, one of the biggest oil refinery complexes in the world, with a total capacity of 955,000 barrels per day.

The facility is operated by state-owned PDVSA.